UV-resistant superhydrophobic coating compositions

ABSTRACT

A coating composition for a substrate includes a polymer binder, one or more hydrophobic silicon dioxide compositions, and one or more UV protection agents. The polymer binder can include a fluoropolymer or an epoxy polymer resin. The coating composition can also include molybdenum disulfide.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/015,771, filed Jun. 23, 2014, entitled “UV-ResistantSuperhydrophobic Coating Compositions,” the entire disclosure of whichis incorporated herein by reference.

FIELD

The present invention relates to coatings for substrates such asconductors, including bare overhead conductors for overhead powertransmission lines and bare grounding wires.

BACKGROUND

Overhead power transmission lines provide electrical power transmissionand distribution over great distances. The power transmission lines aretypically supported via towers and/or poles so as to be suspended at asafe distance from the ground so as to prevent dangerous contact with anenergized line during power transmission operations.

It is desirable to provide an adequate coating for substrates, such asconductors, that is resistant to accumulation of ice, effective inrepelling water, self-cleaning, as well as resistant to wear from theoutside environment (for example, due to UV exposure as well as exposureto acid rain and other pollutants).

SUMMARY

A coating composition comprises a polymer binder, one or morehydrophobic silicon dioxide compositions, and one or more UV protectionagents. The polymer binder can include a fluoropolymer or an epoxypolymer resin. In one example embodiment, the polymer binder comprisesone or more fluoropolymers. In another example embodiment, the polymerbinder comprises one or more epoxy polymer resins. In still a furtherexample embodiment, the polymer binder comprises a mixture of one ormore fluoropolymers and one or more epoxy polymer resins. In anembodiment, the coating composition can also include molybdenumdisulfide. The coating composition is applied to a substrate surface,such as the exterior surface of a bare overhead conductor.

These and/or other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a side view in partial cross section depicting analuminum conductor steel supported (ACSS) round wire (RW) conductorcable to which a coating as described herein is applied.

FIG. 2 depicts a side view in partial cross section depicting analuminum conductor steel supported (ACSS) trap wire (TW) conductor cableto which a coating as described herein is applied.

FIG. 3 depicts a side view in partial cross section depicting theconductor cable of FIG. 1 including a coating composition of the typedescribed herein.

DETAILED DESCRIPTION

As described herein, UV-resistant superhydrophobic coatings forconductors are formed from novel compositions having heat and chemicalresistant properties, being permeation resistant, and having asufficient hardness and toughness while also a suitable flexibility andare suitably lightweight. The coating compositions can also be impartedwith abrasion resistant properties. The coating compositions cancomprise a hydrophobic polymer binder, one or more hydrophobic silicacompositions, a friction reducing agent and/or one or more UV protectionagents. As described herein, the coating compositions can be applied toa substrate surface via any suitable technique, such as a wet technique(for example, spray coating, brushing, rolling or any other suitable wetapplication) and a dry technique (for example, a dry powder coating).

The coating compositions are particularly suitable for electricaltransmission cables for the overhead transmission of electricity, suchas bare overhead conductors typically used in power transmission lines(i.e., overhead power lines suspended above ground). Examples of typesof bare overhead conductors to which the coating compositions of thepresent invention can be applied include, without limitation, aluminumconductor steel supported (ACSS) cables, aluminum conductor steelreinforced (ACSR) cables, aluminum conductor steel supported (ACSS)cables, aluminum conductor composite reinforced (ACCR) cables, andaluminum conductor composite core (ACCC) cables, each of which mayinclude electrical strands or wires of the round wire (RW) type, trapwire (TW) type and/or any other suitable conductor types. For example,the coating compositions can be provided for bare overhead conductortypes including, without limitation, ACSS/AW conductors, ACSR/TWconductors, ACSR/RW conductors, ACSR/AW conductors, AAC conductors,AAC/TW conductors, ACAR conductors, AAAC conductors, Motion-Resistantconductors, as well as other types of conductors including, withoutlimitation conductors commercially available under the trade names VR2®,HS285 and C⁷ from Southwire Company (Georgia USA).

The conductors can include any one or combinations of aluminum, aluminumalloys, copper, copper alloys, steel, steel alloys, polymer composites(e.g., a carbon fiber polymer composite core that comprises carbonfibers embedded within a polymer matrix, such as a thermoplastic polymermatrix, where the carbon fiber polymer composite core may be of thetypes described in U.S. Pat. No. 9,012,781, the disclosure of which isincorporated herein by reference in its entirety) and/or any othersuitable types of conductive or non-conductive materials making up theconductor core and/or any other portions of the conductor. It is furthernoted that the coating compositions can also be applied to any othersubstrates to provide superhydrophobicity and UV protection for suchsubstrates. The conductors can include a core member that can compriseone or more electrically conductive strands or wires that extend thelength of the conductors, where the conductive wires can be arranged inany suitable configurations or arrays along a central axis of theconductors. For example, a conductor can include a core member thatcomprises one or more layers of wires, where the wires in each layer arearranged in any suitable manner (e.g., twisted with each other, wrappedtogether in the layer with each other, etc.). The core member canfurther include a single central strand or wire at the center of thecore member with one or more layers of wires extending around thecentral wire. Further still, the core member can include a core cable orstrand (which may be conductive or non-conductive) and one or moreelectrically conductive strands or wires extending around the core cableor strand. The conductive wires and/or core cable or strand can have anysuitable dimensions, including wires having cross-sectional dimensions(i.e., a dimensions transverse the length of the wires, such asdiameters for wires having circular cross-sections) that are from about1 mm or smaller to about 5 cm or greater. The outer transversecross-section (e.g., outer diameter) of a conductor can also varyconsiderably based upon a particular application, where some conductorscan have diameters of about 5 cm or smaller to about 30 cm or greater.

An example embodiment of an ACSS RW cable is depicted in FIG. 1, whilean example embodiment of an ACSS TW cable is depicted in FIG. 2. In eachembodiment, the ACSS cable includes concentrically aligned or layeredstrands or wires with a central or core portion 2 of the cable includingsteel wires and two or more layers of aluminum wires 4 circumferentiallyaligned around the core portion of steel wires (for example, thealuminum wires can have a 1350-0 (fully annealed to soft) temper. Thealuminum wires 4-1 have a circular or round configuration as shown forthe ACSS RW cable type depicted in FIG. 1, while at least some of thealuminum wires 4-2 have a generally trapezoidal shape for the ACSS TWcable type depicted in FIG. 2. The steel and aluminum wires within thecables can be coated with an alloy or any other suitable coating toprevent corrosion and provide other protection for the wires as well asenhance power transmission capabilities within the cables. In addition,the wires within the cables can comprise pure aluminum, one or morealuminum alloys, copper and/or other suitable electrically conductingmaterials to enhance power transmission capabilities. The core wires cancomprise steel, coated steel, aluminum, aluminum alloys, and/or othercomposite materials. The coating composition can further be applied tothe outer most layer and/or to one or more of the individual wires ofthe conductor. The conductor can be a solid single conductor (forexample a bare grounding wire, such as a bare grounding copper wire) ormulti-stranded conductor. The stranded conductor can comprise a singlelayer of wires or multiple layers of wires. Specific ACSS RW and ACSS TWcable types are commercially available from, for example, SouthwireCompany (Georgia USA). The ACSS cables are designed for use in overheadpower distribution lines, where such cables are configured to operatecontinuously at elevated temperatures of up to about 250° C. withoutloss of strength. It is further noted that these cable types areprovided for purposes of illustration only, and the coatings describedherein are not limited to implementation with only these cable types butinstead can be used to coat any other types of bare overhead conductorsas well as other types of conductors.

The conductor coating compositions comprise a polymeric base or binder,such as a hydrophobic polymer base or binder. Preferably types ofpolymeric binders suitable for forming coating compositions inaccordance with the present invention include thermoplasticfluoropolymers and thermosetting polymer resins (such as epoxy polymerresins). For example, the polymer binder can comprise one or morefluoropolymers, the polymer binder can comprise one or more epoxypolymer resins, or the polymer binder can comprise a mixture of one ormore fluoropolymers and one or more epoxy polymer resins.

The polymer binder material should be suitably stable at a wide range oftemperatures, depending upon different applications for use of thecoating compositions. For example, coating compositions for conductorsneed to have a sufficiently high thermal stability or rating in order towithstand elevated temperatures of the conductor member (e.g., due tothe electrical load or current running through the conductor member).The onset or softening of the polymer binder material, also referred toas its glass transition temperature (T_(g)) and/or the meltingtemperature (T_(m)) of the polymer binder (i.e., the temperature pointat which the polymer changes from solid to liquid) must be great enoughto withstand heat dissipated from the internal conductor member.Suitable T_(g) or T_(m) values for polymer binder materials comprisingfluoropolymers and/or epoxy polymer resins can be from about 75° C. toabout 350° C., such as from about 100° C. to about 300° C., from about150° C. to about 280° C. and/or from about 200° C. to about 250° C.

The polymer binder comprises a major portion (i.e., 50% or greater byweight of the coating composition) of the coating compositions. Inparticular, the polymer binder can comprise at least about 60% by weightof the coating composition, at least about 70% by weight of the coatingcomposition, at least about 80% by weight of the coating composition, orat least about 90% by weight of the coating composition.

Some non-limiting examples of suitable types of thermoplasticfluoropolymer binders for implementation as part of the coatingcompositions include polytetrafluoroethylene (PTFE), polyvinylidenedifluoride (PVDF), polyhexafluoropropylene (PHFP), and combinationsthereof (for example, one or any combination of PTFE, PVDF and PHFP).Some specific examples of fluoropolymers suitable for forming binders ofthe coating compositions of the present invention and which include oneor more of PTFE, PVDF and PHFP are commercially available under thetrade names DYNEON THV 500G (3M Corporation), DYNEON FEP 6322 (3MCorporation), Dupont FEP 9494 (DuPont Corporation), and Dupont FEP 106(Dupont Corporation). The DYNEON THV fluoropolymer composition comprisesPTFE, PVDF and PHFP, while the FEP fluoropolymer compositions comprisePTFE and PHFP. In an example embodiment, the fluoropolymer binderincludes THV fluoropolymers (PTFE, PVDF and PHFP) in an amount of about0% to about 70% by weight of the binder and FEP fluoropolymers (PTFE andPHFP) in an amount of about 30% to about 90% by weight of the binder. Inanother example embodiment, the fluoropolymer binder is made up entirelyor almost entirely of FEP fluoropolymers (PTFE and PHFP).

Some non-limiting examples of suitable types of thermosetting polymerresins for implementation as part of the coating compositions are epoxypolymer resins such as glycidyl epoxy polymer resins and non-glycidylepoxy polymer resins. Glycidyl epoxy polymer resins can be prepared viaa condensation reaction of a suitable dihydroxy compound, dibasic acidor a diamine with epichlorohydrin, while non-glycidyl epoxy polymerresins can be formed by peroxidation of an olefinic double bond in asuitable polymer compound. Glycidyl epoxy polymer resins can includeglycidyl-amine polymer combinations, glycidyl-ester polymer combinationsand glycidyl-ether polymer combinations. Some specific examples ofglycidyl epoxy polymer resins include, without limitation, bisphenol Aepoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, andnovolac (phenol-formaldehyde) epoxy resins. Non-glycidyl epoxy polymerresins can include aliphatic polymers and/or cycloaliphatic polymers.Suitable thermosetting epoxy polymer resins for use in forming coatingcompositions can include any one or more types of glycidyl epoxypolymers, any one or more types of non-glycidyl epoxy polymers, and anyone or more combinations of glycidyl and non-glycidyl epoxy polymers,where the epoxy polymer resins can further include any number ofsuitable functional groups (e.g., aliphatic and aromatic groups) formingpart of the chemical structure of the epoxy polymer resins.

The selection of one or more particular thermosetting epoxy polymerresins for use as some or all of the polymer binder of the coatingcomposition will depend upon a particular application of use for thecoating composition. Epoxy polymer resins can be selected that aresingle or one-part epoxy resins (i.e., resin only) or two-part epoxyresins (i.e., resin with a further additive such as a catalyst or ahardener), where the curing of the epoxy polymer resin can be at anydesired temperature, including ambient temperature (e.g., from about 20°C. to about 27° C.) or any elevated temperature (e.g., curingtemperatures as high as about 280° C.). Epoxy polymer resins can also beselected for use as some or all of the polymer binder of the coatingcomposition that are cured via a radiation curing (e.g., ultraviolet orUV curing) process, in which the curing process is initiated to cure theepoxy polymer resin by subjecting the epoxy polymer resin to irradiation(e.g., UV radiation).

Any suitable one or more types of solvents may be utilized to providethe epoxy polymer resin in a liquid state for application to a surfaceto be coated (i.e., prior to curing). Alternatively, the epoxy polymerresin can be substantially free of any solvent or solvent-free (e.g., nogreater than about 5% by weight, such as no greater than 1% by weight,of any solvent combined with the epoxy polymer resin to form the polymerbinder).

Choosing one or more particular solvents and/or one or more types ofparticular epoxy polymer resin compounds can be based upon a particularviscosity of the epoxy polymer resin material desired for application toa surface to be coated. In particular, a wide range of viscositiesand/or thermosetting or curing temperature profiles (i.e., temperaturevs. time) can be obtained based upon choosing one or a combination ofspecific epoxy polymer resins (e.g., based upon a specific epoxychemical family, a specific polymer structure and/or one or morespecific polymer functional groups attached with epoxy polymer) and/orone or more solvents combined with such epoxy polymer resins, such thata desired viscosity and/or curing temperature profile can be obtainedbased upon a particular application in which the coating composition isto be applied to a substrate surface. The curing of the one or moreepoxy polymer resins (which includes polymerization reactions of polymerfunctional groups resulting in a certain degree of crosslinking andincrease in viscosity) to achieve a thermoset or cured structure can beadjusted based upon the selection of epoxy polymer resin type(s). Inparticular, epoxy polymer resin type(s) can be selected such that thecoating composition is thermoset or cured at any suitable temperatureand cure time based upon a particular application. For example, for someapplications it may be desirable to achieve curing of the epoxy polymerresin within the coating composition at a lower (e.g., ambient)temperature, while for other applications it may be desirable to achievecuring at an elevated or higher temperature. Typically, curing of anepoxy polymer resin at an elevated temperature will correspond with afaster cure time (i.e., an accelerated curing process).

In addition, the selection of one or a combination (e.g., a blend) ofepoxy polymer resin compounds can be selected based upon desiredproperties for the resultant coating compositions, such as mechanicalproperties, high thermal integrity (e.g., able to withstand sufficientlyhigh temperatures without degradation), corrosion resistance in outdooror other harsh (e.g., extreme upper and/or lower temperature)environments, etc., for a particular application (e.g., for coatingoverhead power transmission lines as described herein).

Given the variety of different types of epoxy polymer resins and varyingchemical and mechanical properties associated with the varying types,one or more particular types of epoxy polymer resins can be selected forforming the polymer binder of the coating compositions so as to impartdesired properties such as curing profile, thermal stability andcorrosion resistance for the coating compositions (particular forcoating compositions for use on surfaces subjected to exposure withinharsh outside environments).

Epoxy polymer resins can be provided in a liquid state (i.e., prior tocuring), e.g., via combining with one or more solvents, so as tofacilitate ease of mixing or combining with other additives orcomponents to form the coating compositions (e.g., combining withhydrophobic silicon dioxide compositions, a friction reducing agent suchas molybdenum disulfide and/or UV protection agents) so as to achieve asubstantially homogeneous dispersion of the other components within theliquid epoxy polymer resins prior to coating and curing on a substratesurface. Further, the coating compositions comprising one or more epoxypolymer resins in liquid state can be applied to a substrate surface inany suitable manner including, without limitation, via a roller, via abrush, via a suitable spraying technique (e.g., via a spray gun), viadipping or submersion of the substrate surface within a bath orreservoir containing the coating compositions, etc.

Some examples of suitable epoxy polymer resins that can be used aspolymer binders within coating compositions as described herein includeepoxy polymer resins having a viscosity at an ambient temperature (e.g.,from about 20° C. to about 27° C.) and prior to initiation (and/or atthe initial onset) of curing in the range from about 1 centipoise (cP)to about 25,000 cP, such as from about 50 cP to about 15,000 cP, or fromabout 100 cP to about 11,000 cP, and further still from about 200 cP toabout 6,000 cP.

Other examples of suitable epoxy polymer resins that can be used aspolymer binders within coating compositions as described herein includeepoxy polymer resins having curing schedules as follows: a curing time(e.g., a time from initial onset of curing at an initial viscosity ofthe epoxy polymer resin to a final cured or thermoset state at a finalviscosity of the epoxy polymer resin that is greater than the initialviscosity) from about 5 hours to about 2 weeks, such as from about 12hours to about 1 week and/or from about 24 hours to about 48 hours, at acuring temperature (e.g., a temperature at which activation of thecuring process for the epoxy polymer resin occurs) that is ambient(e.g., from about 20° C. to about 27° C.); a curing time of no greaterthan about 4 hours at a curing temperature in the range from about 200°C. to about 280° C. (e.g., a temperature of about 250° C.); a curingtime of no greater than about 1 hour at a curing temperature from about200° C. to about 280° C. (e.g., a temperature of about 250° C.); and acuring time of no greater than about 30 minutes (e.g., 20 minutes orless) at a curing temperature from about 200° C. to about 280° C. (e.g.,a temperature of about 250° C.).

Some specific examples of thermosetting epoxy polymer resins that can beused as polymer binders within coating compositions as described hereininclude, without limitation: two part epoxy polymer resins commerciallyavailable under the trade names Resolcoat GC-HT210, Resolcoat GC-HT180,Resolcoat HTG 240, Resolcoat HTG 210 and Resolcoat HTG 180 (Resoltech,France); single or one-part epoxy polymer resins commercially availableunder the trade names Supreme 10HT, Supreme 3HT-80, and SupremeEP17HT-LO and a two-part epoxy polymer resin commercially availableunder the trade name Supreme 45HTQ (Masterbond, Inc., New Jersey, USA);two-part epoxy polymer resins commercially available under the tradenames Hysol® 9340 and E-90FL™ (Loctite Corporation, Connecticut, USA);single or one-part epoxy polymer resins commercially available under thetrade names Duralco™ 4538, Duralco™ 4525 and Duralco™ 4461 (CotronicsCorporation, New York, USA); and single or one-part epoxy polymer resinscommercially available under the trade names BONDiT™ B-46, BONDiT™ B-45,BONDiT™ B-482, BONDiT™ B481 and BONDiT™ B-4811 (Reltek LLC, California,USA).

The polymer binders described herein (i.e., fluoropolymers and/or epoxypolymer resins) can be selected to be hydrophobic and thus waterrepellant. The hydrophobicity of coatings formed utilizing such polymerbinders can be described in relation to a contact angle of a waterdroplet formed on a surface of the coating. In particular, a waterdroplet formed on a coating of the present invention has a contact angleof greater than 90°. The greater the degree of the contact angle of awater droplet formed on the coating surface correlates with a greaterdegree of hydrophobicity (i.e., more hydrophobic). The polymer binderscan be formed utilizing one or more fluoropolymers, one or more epoxypolymer resins and/or combinations of one or more fluoropolymers withone or more epoxy polymer resins, where a particular polymer binder canbe utilized that results in desired properties for the coatingcomposition including a desired hydrophobicity (e.g., as defined bycontact angle of a water droplet formed on a surface of the coatingcomposition applied to a substrate).

In addition to the selection of a suitable polymer binder that includesone or a combination of fluoropolymers and/or one or a combination ofepoxy polymer resins, hydrophobicity of the coating composition can beenhanced (i.e., contact angle of water droplet on coating surface isincreased) by providing within the coating compositions hydrophobicsilicon dioxide or silica (hydrophobic SiO₂), in particular hydrophobicfumed or pyrogenic silica. The hydrophobic SiO₂ can be provided in anamount of no greater than about 15% by weight of the coatingcomposition, for example in an amount from about 0.5% to about 15% byweight of the coating composition, or an amount from about 0.5% to about9% by weight of the coating composition.

As used herein, the term “hydrophobic silica” or “hydrophobic silicacomposition” refers to silica (i.e., silicon dioxide) that has beentreated with organic surfactants and/or polymers so as to bondhydrophobic functional groups to silica thus yielding a compositionhaving a degree of hydrophobicity that is greater (i.e., morehydrophobic) in relation to silica prior to treatment. For example,silica can be hydrophobized to include any one or more functionalpolymer groups including, without limitation, alkyl, alkoxy, silyl,alkoxysilyl, siloxy, bonded to the surface of the silica to obtain ahydrophobic fumed or pyrogenic silica. The hydrophobic silica can alsobe formed from fumed or pyrogenic silica, which is silica produced viaflame pyrolysis of, e.g., silicon tetrachloride or quartz sand. Fumed orpyrogenic silica comprises amorphous silica that is fused into branchedparticles resulting in a powder having low bulk density and high surfacearea. In example embodiments, the hydrophobic silica can have a BET(Brunauer, Emmett and Teller) surface area from about 80 m²/g to about300 m²/g. In other example embodiments, the hydrophobic silica can havea carbon content greater than zero (where a carbon content of zerorepresents silica that has not been treated with carbon-containingpolymers), such as a carbon content of at least about 0.5% by weight, acarbon content of at least about 1.0% by weight, or a carbon content ofat least about 1.5% by weight. For example, the hydrophobic silica canhave a carbon content from about 0.5% by weight to about 7.0% by weight.

Some specific examples of polymer functional groups suitable for bondingwith silica (and/or fumed or pyrogenic silica) to form a hydrophobicsilica for use in coating compositions as described herein includemethyl chlorosilanes, hexamethyldisilazane (HMDS), polydimethylsiloxane(PDMS), octylsilane, hexadecylsilane, methacrylsilane,dimethyldichlorosilane (DDS), and octamethylcyclotetrasiloxane.Selection of one or more specific types of hydrophobic silica, each ofwhich includes specific functional groups, to add to the coatingcompositions will control the amount or degree at which hydrophobicityof the coating compositions can be modified. In other words, thehydrophobicity of the coating compositions can be precisely modified or“fine tuned” based upon the selection of one or more specific types ofhydrophobic silica compositions, as well as the amount, to add to thecoating compositions.

Some non-limiting specific examples of various grades of one or moresuitable hydrophobic silica compositions that can be added to thecoating compositions of the present invention are: hydrophobic silicacompositions having HMDS, PDMS, octylsilane, hexadecylsilane,methacrylsilane, DDS or octamethylcyclotetrasiloxane as a functionalgroup and commercially available under the trade names AEROSIL R 104,AEROSIL R 106, AEROSIL R 202, AEROSIL R 208, AEROSIL R 504, AEROSIL R711, AEROSIL R 805, AEROSIL R 812, AEROSIL R 812S, AEROSIL R 972,AEROSIL R 974, AEROSIL R816 AEROSIL R 7200 and AEROSIL R 8200 (EvonikIndustries AG, Germany); hydrophobic silica compositions having methylchlorosilanes or HMDS as a functional group and commercially availableunder the trade names HDK H13L, HDK H15, HDK H17, HDK H18, HDK H20, HDKH30 and HDK H2000 (Wacker Chemie AG, Germany); and hydrophobic silicacompositions having HMDS, DDS or PDMS as a functional group andcommercially available under the trade names CAB-O-SIL TS-530, CAB-O-SILTS-610, CAB-O-SIL TS-622 and CAB-O-SIL TS-720 (Cabot Corporation,Georgia, USA).

Providing one or more hydrophobic silica compositions within the coatingcomposition results in an increase in the contact angle for a waterdroplet formed on the composition coated on a substrate surface to 130°or greater (for example, at least about 140°, at least about 150°, atleast about 160° or even greater), thus rendering the coatingcomposition superhydrophobic.

The coating compositions can further be enhanced by providing a frictionreducing agent such as molybdenum disulfide (MoS₂). The frictionreducing agent lowers the coefficient of friction of the coatingcomposition so as to render the coating compositions more durable andresistant to wear caused by abrasion on the coating surface. Forexample, in embodiments in which the coating compositions are applied toconductor surfaces, the friction reducing agent added to the coatingcompositions minimizes damage to the coating during installation of theconductors. The friction reducing agent can be provided in an amountfrom about 0.1% to about 15% by weight of the coating composition (forexample, from about 0.1% to about 10% by weight of the coatingcomposition, or from about 5% to about 10% by weight of the coatingcomposition). Some non-limiting examples of suitable friction reducingagents in the form of molybdenum disulfide that can be added to thecoating compositions of the present invention are a product commerciallyavailable under the trade name MCLUBE (McGee Industries) and MoS₂products commercially available from Noah Technologies Corporation(Texas USA).

At least one UV protection agent, such as zinc oxide (ZnO) or titaniumdioxide (TiO₂) can also be provided in the coating compositions toprovide enhanced UV protection and wear resistance against sunlight andother external environment elements, such that the coating compositionmaintains or substantially maintains its hydrophobic properties evenafter long periods of exposure to UV radiation. The one or more UVprotection agents can be provided in an amount of about 0.1% to about10% by weight of the coating composition, such as from about 0.1% toabout 6% by weight of the coating composition. Some non-limitingexamples of zinc oxide products that can be provided in the coatingcompositions are commercially available under the trade names ZANO(Umicore Zinc Chemicals) and Z-COTE (BASF Corporation).

Coating compositions can be formed by mixing the components as describedherein (polymer binder, one or more hydrophobic silica compositions, oneor more UV protection agents and/or friction reducing agent) in anysuitable manner with a suitable carrier solution (e.g., isopropylalcohol) or any other suitable organic solution/solvent that adequatelydisperses (e.g., facilitates a homogeneous dispersion of components)and/or dissolves the components within solution. The mixture can then beapplied to the conductor (or any other suitable) surface utilizing anysuitable application technique (e.g., spray coating, application via aroller or brush, immersion of the substrate surface in the solutionmixture, etc.).

When utilizing a fluoropolymer binder, the applied coating is thensufficiently dried to remove the liquid carrier thus resulting in a drypowder coating being adhered to the surface. After drying, the substrateis baked at a suitable temperature close to or above the melting pointof the fluoropolymer binder for a suitable time period to allow thecomposition to flow and adhere properly to the substrate surface uponcooling, thus obtaining the resultant coating composition on thesubstrate. When utilizing an epoxy polymer resin, the applied coating iscured at a suitable curing temperature and for a sufficient time periodto thermoset the epoxy polymer. When utilizing a combination of one ormore fluoropolymers and one or more epoxy polymer resins for the polymerbinder, and suitable combination of drying and/or heating may be appliedto achieve suitable curing of the epoxy polymer component(s) within thebinder as well as suitable flow, solidification and adherence of thefluoropolymer component(s) within the binder.

Some non-limiting examples of forming coating compositions in accordancewith the present invention are described in Examples 1-5. In particular,Examples 1-4 describe the formation of coating compositions that includepolymer binders comprising one or more fluoropolymers, where suchcoating compositions are further applied to a substrate surface. Example5 describes the formation of coating compositions that include polymerbinders comprising one or more epoxy polymer resins.

Example 1

Forty five grams of Dyneon THV 500G flouropolymer (3M Corporation) wascombined with 45 grams of Dupont FEP 9494 flouropolymer (DupontCorporation), 5 grams of AEROSIL R 8200 fumed silica (Evonik IndustriesAG), 5 grams McLube MOS2-98 molybdenum disulfide (McGee Industries) and1 gram of Zano 20 zinc oxide (Umicore Zinc Chemicals) within 150 gramsisopropyl alcohol carrier solution. The components were suitably mixedwithin solution to ensure a relatively homogeneous combination of thecomponents existed in solution.

Aluminum plate samples were coated with the solution (for example, byspraying the coating to the surfaces of the plates), where the coatingthickness on each plate was in the range from about 3 mil to about 8mil. The surface coated plates were dried at ambient temperature (forexample, about 25° C.) for at least 30 minutes followed by baking theplates in an air-circulated oven at a temperature of about 300° C. forabout 10 minutes. The resultant coating composition adhered to thealuminum plate samples had the following composition:

TABLE 1 Dyneon THV 500G (fluoropolymers) 45 wt %  Dupont FEP 9494(fluoropolymers) 45 wt %  AEROSIL R 8200 (hydrophobic fumed 4 wt %silica) McLube MoS2-98 (molybdenum disulfide) 5 wt % Zano 20 (zincoxide) 1 wt %

The contact angle for water droplets was measured for the coatingcompositions formed on the aluminum plates. The measured contact angleswere at least about 140°, with some contact angles being greater thanabout 150° (e.g., as high as about 160° or greater).

Example 2

A composition was formed and applied to aluminum plates in a similarmanner as described for Example 1, with the exception that certaincomponents and weight compositions were modified such that the resultantcoating composition was as follows:

TABLE 2 Dyneon THV 500G (fluoropolymers) 67 wt % Dupont FEP 9494(fluoropolymers) 10 wt % Dupont FEP 106 (fluoropolymers) 10 wt % AEROSILR 812S (hydrophobic fumed  6 wt % silica) McLube MoS2-100 (molybdenum  4wt % disulfide) Zano 20 Plus (zinc oxide)  3 wt %

Example 3

A composition was formed and applied to aluminum plates in a similarmanner as described for Example 1, with the exception that certaincomponents and weight compositions were modified such that the resultantcoating composition was as follows:

TABLE 3 Dupont FEP 106 (fluoropolymers) 82 wt %  AEROSIL R 812S(hydrophobic fumed 5 wt % silica) AEROSIL R 8200 (hydrophobic fumed 3 wt% silica) McLube MoS2-99 (molybdenum disulfide) 8 wt % Z-cote HP1 (zincoxide) 2 wt %

Example 4

Compositions were formed and applied to aluminum plates in a similarmanner as described for Example 1, with the exception that certaincomponents and weight compositions were modified such that the resultantcoating compositions and average contact angle values measured were asfollows:

TABLE 4 Composition A Composition B Composition C Dupont FEP 84.63 wt % 86.45 wt %  81.90 wt %  6322 PZ (fluoropolymers) AEROSIL 5.58 wt % 5.70wt % 5.40 wt % R812S (hydrophobic fumed silica) Zano 20 (zinc 2.79 wt %2.85 wt % 2.70 wt % oxide) MOS2 99 7.00 wt % 5.00 wt % 10.00 wt % (molybdenum disulfide) Average Contact 155.0 148.6 144.3 Angle

While the previous examples show the application of the coatingcompositions to aluminum surfaces, it is noted that the compositions canbe applied to any metal or other (for example, organic) substratesurface, particularly substrate surfaces capable of withstanding dryingtemperatures (for example, 300° C.) that ensure sufficient melting ofthe fluoropolymer binder to form a homogeneous coating composition.

Example 5

A plurality of epoxy polymer resin based coating compositions (fifteentotal) were prepared by combining the following epoxy polymer resins inliquid state with hydrophobic silica, zinc oxide and molybdenumdisulfide in the following weight percentage ratios:

TABLE 5 Compositions 1-3 Composition Composition Composition 1 2 3Resolcoat GC-HT210 41.0 wt %  57.0 wt %  80.0 wt %  (2-part epoxypolymer binder) Resolcoat GC-HT180 41.0 wt %  29.0 wt %  10.0 wt % (2-part epoxy polymer binder) Wacker HDK H13L 4.5 wt % 3.5 wt % 2.5 wt %(hydrophobic silica) BASF Z-COTE HP1 (zinc 10.0 wt %  8.0 wt % 6.0 wt %oxide) McLube MoS2-100 3.5 wt % 2.5 wt % 1.5 wt % (molybdenum disulfide)Total 100 wt %  100 wt %  100 wt %  Compositions 4-6 CompositionComposition Composition 4 5 6 Masterbond Supreme 10HT 78.0 wt %  84.0 wt%  89.0 wt %  (1-part epoxy polymer binder) Cabot CAB-O-SIL TS-610 7.0wt % 5.0 wt % 3.0 wt % (hydrophobic silica) BASF Z-COTE (zinc 5.5 wt %4.0 wt % 2.5 wt % oxide) McLube MoS2-100 9.5 wt % 7.0 wt % 5.5 wt %(molybdenum disulfide) Total 100 wt %  100 wt %  100 wt %  Compositions7-9 Composition Composition Composition 7 8 9 Loctite Hysol 9340 (2-part78.0 wt %  83.0 wt %  86.0 wt %  epoxy polymer binder) Wacker HDK H1710.0 wt %  9.0 wt % 8.0 wt % (hydrophobic silica) BASF Z-COTE HP1 (zinc8.0 wt % 6.0 wt % 4.5 wt % oxide) McLube MoS2-100 4.0 wt % 2.0 wt % 1.5wt % (molybdenum disulfide) Total 100 wt %  100 wt %  100 wt % Compositions 10-12 Composition Composition Composition 10 11 12Cotronics Duralco 4461 83.5 wt %  83.5 wt %  83.5 wt %  (1-part epoxypolymer binder) Cabot CAB-O-SIL TS-720 8.0 wt % 7.0 wt % 6.0 wt %(hydrophobic silica) BASF Z-COTE (zinc 5.0 wt % 4.0 wt % 3.0 wt % oxide)McLube MoS2-99 3.5 wt % 5.5 wt % 7.5 wt % (molybdenum disulfide) Total100 wt %  100 wt %  100 wt %  Compositions 13-15 Composition CompositionComposition 13 14 15 Reltek BONDiT B-481 40.0 wt %  54.0 wt %  76.0 wt%  (1-part epoxy polymer binder) Reltek BONDiT B-46 (1- 40.0 wt %  29.5wt %  12.0 wt %  part epoxy polymer binder) Wacker HDK H20 6.0 wt % 5.0wt % 4.0 wt % (hydrophobic silica) BASF Z-COTE HP1 (zinc 11.0 wt %  9.0wt % 7.0 wt % oxide) McLube MoS2-99 3.0 wt % 2.5 wt % 1.0 wt %(molybdenum disulfide) Total 100 wt %  100 wt %  100 wt % 

Each of the coating compositions of Example 5 including the one or moreepoxy polymer binders can be coated on a substrate surface via anysuitable application technique, such as using a brush or roller. Afterapplication, the coating compositions are cured at suitable curingprofiles (i.e., suitable curing temperature and time), depending uponthe specifications associated with the different types of epoxy polymerbinders used.

The resultant coating compositions provide effective hydrophobicity forthe substrate surfaces to which they are applied (e.g., a contact anglefor a water droplet on the coated substrate surface is greater than 90°,typically at least about 140°).

Coating compositions as described herein can be applied to the exteriorsurface, or portions thereof, of conductors (for example, to a roundedor circular exterior surface) in the same manner as described herein inrelation to Examples 1-4, where the coating composition can be formed incarrier solution and/or a solvent and then applied, for example, byspray coating, roller coating, brush coating or dipping of a conductorto coat exterior surface portions of the conductor followed by drying(for example air drying and/or heat drying) and/or curing for a suitabletime period to result in the dried and/or thermoset or cured coatingcomposition being adhered to the conductor surface.

In an alternative embodiment, a dry powder coating technique may beutilized to deposit the coating as a powder mixture of the componentsand then heating or baking the conductor (for example, at 300° C. for asufficient time period, for example, about 10 minutes) to result inadhering of the coating composition to the conductor exterior surface.

The coating compositions provide excellent UV protection, in which thehydrophobicity and other coating composition characteristics aresubstantially maintained or un-altered despite long term exposure to UVradiation. The following examples show the effect of exposure to UVradiation to the hydrophobicity of the coating composition.

Example 6

Four samples of Composition A from Example 4 were subjected to UVradiation at a dosage of about 1.05 Watts per square meter (W/m²) for aperiod of 350 hours, with a measurement of contact angle associated witheach sample being recorded at the start (before UV exposure) and after350 hours of UV exposure:

TABLE 6 UV Aging Time (hours of Average Contact Angle exposure at 1.05W/m²) Sample 1 Sample 2 Sample 3 Sample 4 0 154.4 153.4 157.2 158.8 350153.2 150.5 154.4 153.4

As indicated by the results, the level of hydrophobicity (indicated bymeasured average contact angle) of the coating composition sampleschanged only to a small amount or degree after 350 hours of exposure toUV radiation.

Example 7

The following compositions were prepared and coated on aluminumsubstrates in a similar manner as described for Example 1, but withoutmolybdenum disulfide provided in the composition. The compositions weresubjected to UV radiation at a dosage of about 1.05 W/m² for a period upto 470 hours, with a measurement of contact angle associated with eachcomposition being recorded at the start (before UV exposure) and atvarious times up to 470 hours of UV exposure:

TABLE 7 Composition 1 Composition 2 Dupont FEP 6322 PZ 91 wt %  91 wt % (fluoropolymers) AEROSIL R812S 6 wt % 6 wt % (hydrophobic fumed silica)Zano 20 (zinc oxide) 3 wt % 0 wt % Zano 20 Plus (zinc oxide) 0 wt % 3 wt% Average Contact Average Contact UV Aging Time (hours) at Angle forAngle for 1.05 W/m² Composition 1 Composition 2 0 156.9 141.9 50 153.7154.6 100 156.6 157.6 150 152.0 144.2 470 149.8 149.7 670 158.2 153.91270 143.7 144.0 2470 143.8 146.9

The results indicate that a coating composition that includes one ormore polymer binders, such as fluoropolymers, a UV protection agent(such as zinc oxide) and hydrophobic silica provides excellent UVprotection in addition to excellent hydrophobicity even after a longterm exposure to UV radiation. This is indicated by the measured contactangle data provided in the table above, in which the contact angle forthe two compositions changes only to a small degree after an exposure ofup to 2470 hours of UV radiation.

Coating compositions such as the types of the previous examples can beused for coating a substrate surface in which abrasion resistance maynot be of concern but where hydrophobicity is desired and where suchhydrophobicity does not degrade after long term UV exposure. Forexample, these coating compositions can be applied on the surface ofairplane wings or other structural components where hydrophobicity maybe desired that does not degrade due to UV exposure.

For conductors or other structures having rounded or non-planar surfacesto be coated, adding molybdenum disulfide to the coating compositionfurther enhances the resistance of the composition to abrasion, asindicated by the test data of Example 8:

Example 8

Four coating compositions were prepared and applied to an aluminumsurface in a manner similar to that described in Example 1, where thecomponents of the composition and their weight percentages are set forthin the table below. For each composition, the amount of molybdenumdisulfide was varied to determine the resultant effect on wearing of thecoating composition after being subjected to an abrasion test. Inparticular, a Sutherland rub tester was used using a head that weighed2,711 grams and had a contact area of 1.75 inches by 2 inches. Theabrasion material used for the tester was Rhodes American steel woolwith #3 coarseness. Testing was performed by determining a degree ofsuperhydrophobicity of the same sample over different abrasion times. Inbetween each measured time, the sample was washed with isopropyl alcohol(IPA) to remove any non-adhered material, and then put in a 150° F. ovenhad heated for a sufficient time (e.g., about 2-3 minutes) to ensurecomplete removal of IPA.

A degree of superhydrophobicity was determined in the test by measuringa percentage of area of the abraded coating surface that still exhibitssuperhydrophobic properties vs. a remaining area of the abraded coatingsurface that does not exhibit such superhydrophobic properties. Forexample, prior to starting the abrasion test, each coated surfaceexhibits a degree of superhydrophobicity of 100%, meaning that theentire surface area to be subjected to the abrasion test issuperhydrophobic (for example, the contact angle for a water dropletformed on a surface of the coating is 130° or greater). After eachabrasion time, one side of the coated substrate was elevated at a selectangle from a support surface and a number of water droplets were droppedonto the abraded area at different locations within the abraded area todetermine which sections of the abraded area the water droplets adheredto the surface (indicating a portion or section of the abraded area thatis no longer superhydrophobic) and which sections of the abraded areathe water droplets rolled off and did not adhere to the abraded surface.Thus, for example, a degree of superhydrophobicity of 80% indicatesthat, for 80% of the abraded area of the coated surface, no waterdroplets would adhere to such area (thus indicating that 80% of theabraded area is still superhydrophobic). To state this in an alternativemanner, for 20% of the abraded area of the coated surface, the waterdroplets dropped onto the surface adhered to such abraded area (thusindicating that superhydrophobicity for 20% of the abraded area was lostas a result of degradation or total removal of the coating from suchlocation(s) of the abraded area).

The test data showing the different compositions and the results of theabrasion testing is set forth as follows:

TABLE 8 Composition Composition Composition Composition 1 2 3 4 DupontFEP 91 wt %  88.35 wt %  86.67 wt %  82.73 wt %  6322 PZ (fluoro-polymers) AEROSIL 6 wt % 5.83 wt % 5.71 wt % 5.45 wt % R812S(hydrophobic fumed silica) Zano 20 (zinc 3 wt % 2.91 wt % 2.86 wt % 2.73wt % oxide) Molybdenum 0 wt % 2.91 wt % 4.76 wt % 9.09 wt % disulfideAbrasion Time (minutes) 0.0 100% 100% 100% 100% 1.0 100% 100% 100% 100%3.0 0% 50% 90% 100% 3.5 0% 0% 80% 100% 4.0 0% 0% 0% 100% 4.5 0% 0% 0%80% 5.0 0% 0% 0% 0% 6.0 0% 0% 0% 0%

From the test data, it is evident that molybdenum disulfide providesprotection of the coating compositions against abrasion, with a greateramount of molybdenum disulfide provided in the coating compositionsrendering a more durable composition that can withstand more abrasiveforces for a longer time period while still maintaining some level ofhydrophobicity.

The coating compositions can be applied to conductors (for example, ACSSbare overhead conductors) or other suitable substrates at any suitablethicknesses. Non-limiting example thicknesses for the coatingcompositions that are suitable for overhead bare conductors are fromabout 0.01 mil (0.00001 inch) to about 30 mil (0.030 inch), with apreferred thickness range being from about 1.0 mil (0.0010 inch) toabout 10 mil (0.010 inch). For example, the coating compositions can beapplied to a portion of or the entire exterior surface 6-1 or 6-2 of thecable types depicted in FIGS. 1 and 2. FIG. 3 depicts an exampleembodiment of a coating composition 10 as described herein applied tothe exterior (rounded or non-planar) surface of the conductor of FIG. 1.As previously noted, the coating compositions of the present inventioncan also be applied to one or more individual strands or wires within aconductor (such as any of the previously described ACSS cables), forexample, prior to the individual wires being combined with other wiresto form the conductor. In addition, the coating compositions can beapplied to any one or more types of solid conductors (e.g., a groundwireor any other type of solid conductor) having a variety of differentdiameters or cross-sectional dimensions.

Coating conductors with the coating compositions as described hereinprovide a number of beneficial features in addition to the hydrophobic,UV protection and/or abrasion resistant features. For example, incertain environments in which corrosion may be an issue for overheadconductors (such as near coastal areas where the salt content in the airor surrounding environment is high), the coating compositions asdescribed herein provide a barrier to prevent or significantly limit anycorrosion of the conductor cable exposed to such corrosive environmentalconditions. In other scenarios in which a conductor cable has a metallicsurface that is shiny, conventional techniques apply a processing stepin which the surface is abraded (roughened) to render the surfacenon-specular (so as to eliminate or reduce light reflection by overheadcable lines toward airplanes or other aerial equipment). Utilizing thecoating compositions as described herein to coat conductors alsoalleviates the need for abrading the surface of shiny conductors, sincethe coated conductor provides a non-specular exterior surface for theconductor to which it is coated. Thus, the coating conductors can becoated on a non-abraded surface of a conductor while still providingnon-specular properties for the conductor.

Although the disclosed inventions are illustrated and described hereinas embodied in one or more specific examples, it is nevertheless notintended to be limited to the details shown, since various modificationsmay be made therein without departing from the scope of the inventions.Accordingly, it is appropriate that the invention be construed broadlyand in a manner consistent with the scope of the disclosure.

What is claimed:
 1. A coating composition for a substrate, the coatingcomposition comprising: a polymer binder comprising a fluoropolymer oran epoxy polymer resin; one or more hydrophobic silicon dioxidecompositions; molybdenum disulfide; and one or more UV protectionagents; wherein the coating composition includes at least about 50% byweight of the polymer binder, from about 0.5% to about 15% by weight ofone or more hydrophobic silicon dioxide compositions, from about 0.1% toabout 15% by weight of molybdenum disulfide, and from about 0.1% toabout 10% by weight of one or more UV protection agents.
 2. The coatingcomposition of claim 1, wherein the polymer binder has a glasstransition temperature or a melting point in a range from 75° C. to 350°C.
 3. The coating composition of claim 1, wherein the binder comprisesat least one fluoropolymer selected from the group consisting ofpolytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), andpolyhexafluoropropylene (PHFP).
 4. The coating composition of claim 1,wherein the binder comprises at least one epoxy polymer resin having aviscosity at a temperature from about 20° C. to about 27° C. and priorto initiation of curing in the range from 1 centipoise to 25,000centipoise.
 5. The coating composition of claim 1, wherein at least oneof the UV protection agents comprises zinc oxide.
 6. The coatingcomposition of claim 1, wherein each of the one or more hydrophobicsilicon dioxide compositions comprises at least one functional groupselected from the group consisting of alkyl, alkoxy, silyl, alkoxysilyland siloxy.
 7. A conductor coated with the coating composition ofclaim
 1. 8. A conductor comprising a plurality of stranded wires,wherein at least one stranded wire is coated with the coatingcomposition of claim
 1. 9. The coating composition of claim 1, wherein acontact angle of a water droplet formed on the coating composition is atleast 140° after exposure of the coating composition to UV radiation ofat least about 1 W/m² for a time period of at least about 150 hours. 10.The coating composition of claim 6, wherein each of the one or morefunctional groups is selected from the group consisting of methylchlorosilanes, hexamethyldisilazane (HMDS), polydimethylsiloxane (PDMS),octylsilane, hexadecylsilane, methacrylsilane, dimethyldichlorosilane(DDS), and octamethylcyclotetrasiloxane.
 11. The conductor of claim 7,wherein the conductor comprises a bare overhead conductor.
 12. Theconductor of claim 7, wherein an exterior surface of the conductor iscoated with the coating composition at a thickness from about 0.00001inch to about 0.030 inch.
 13. The conductor of claim 7, wherein theconductor is a grounding bare wire.
 14. The conductor of claim 7,wherein the conductor comprises a solid conductor material comprisingcopper, aluminum or aluminum alloy.
 15. The coating composition of claim9, wherein the contact angle of a water droplet formed on the coatingcomposition is at least 140° after exposure of the coating compositionto UV radiation of at least about 1 W/m² for a time period of at leastabout 470 hours.
 16. The conductor of claim 11, wherein the conductorcomprises aluminum, steel or a carbon fiber polymer composite material.